Silicone-based pressure-sensitive adhesive compositions are superior to other pressure-sensitive adhesives in low-temperature resistance, electrical characteristics, and other properties and, hence, the range of the use of the compositions is increasing in recent years and the demand for the compositions is also increasing steadily.
In general, in the production of a pressure-sensitive tape, a pressure-sensitive adhesive is coated on a tape substrate made of a plastic or other material to form a pressure-sensitive adhesive layer, the coated tape is wound, and rewinding is then conducted in order to slit the coated tape. This process has often had problems that rewinding cannot be conducted smoothly because of troubles such as loud noises made by the rewinding, resulting in a low working efficiency for rewinding, and that the surface smoothness of the pressure-sensitive adhesive layer is impaired by the rewinding and, as a result, rewound tape products have unevenness for adhesion properties.
As an expedient for improving the efficiency of rewinding, a technique of adding a filler, such as calcium carbonate, titanium oxide, zinc oxide, aluminum hydroxide, quartz powder, diatomaceous earth, clay, or silica, to pressure-sensitive adhesives is being employed. However, the addition of such a filler to silicone-based pressure-sensitive adhesives generally impairs adhesion and tackiness. In addition, such silicone-based pressure-sensitive adhesives have had problems that when coated on a substrate, the pressure-sensitive adhesives are less apt to give a smooth coat surface to show poor film-forming properties, and that they have poor transparency.
On the other hand, where a plastic film made of a polyolefin such as polyethylene or polypropylene, a polyester such as poly(ethylene terephthalate), or the like is printed, coated, or subjected to a similar treatment, a treating agent such as a chlorinated polyolefin (JP-B-50-35091), acrylic resin, silane-modified polyolefin (JP-A-56-164858), or the like is being used as a treating agent to form a primer coat on the film surface, in order to improve wettability by or affinity for the printing ink or coating composition to be applied. (The terms "JP-B" and "JP-A" as used herein mean an "examined Japanese patent publication" and an "unexamined published Japanese patent application", respectively.) However, since films having such a primer coat formed thereon generally show poor slip properties, development of a treating agent which gives good slip properties for easy handling has been desired. Although a silicone oil, stearic acid ester, or the like has been added to the treating agents for the purpose of improving slip properties, there has been a problem that the thus-improved slip properties are gradually impaired with the lapse of time. Further, there are cases that even with such a surface treatment, the treated film is not satisfactorily coated or printed according to the kind of the coating composition or printing ink used. Thus, there has also been a desire for a treating agent which can impart better coating suitability to plastic films.